Answer:
To show frustration
Explanation:
As it is stated, adept is a person that is skilled at something, therefore when that person is doing a task, he feels confident. He knows exactly what to do in order to be successful. In this case, the narrator wants to express that he had so many things to think about and calculate that he was not confident, he couldn't achieve his goal and he got frustrated. By using the prefix un-, which means not, he shows us that he felt not prepared enough to succeed. This prefix is used to give opposite and negative meaning to the words.
